Interleukin-13 and -4 expression in the central airways of smokers with chronic bronchitis

The aim of this study was to determine whether the T-helper 2-type cytokines interleukin (IL)-13 and -4 are involved in mucus hypersecretion, the hallmark of chronic bronchitis (CB). Surgical specimens were examined from 33 subjects undergoing lung resection for localised peripheral malignant pulmonary lesions: 21 smokers with symptoms of CB, 10 asymptomatic smokers (AS) and two nonsmokers with normal lung function. The number of IL-4 and -13 positive (+) cells in the central airways was quantified. To better assess the cytokine profile, a count was also made of IL-5+ and interferon (IFN)-gamma+ cells. Compared to AS, the CB group had an increased number of IL-13+ and -4+ cells in the bronchial submucosa, while the number of IL-5+ and IFN-gamma+ cells were similar in all the groups. No significant associations were found between the number of cells expressing IL-13 or -4 and the number of inflammatory cells. Double labelling showed that 13.2 and 12.9% of IL-13+ cells were also CD8+ and CD4+, whereas 7.5 and 5% of IL-4+ cells were CD8+ and CD4+, respectively. In conclusion, T-helper-2 and -1 protein expression is present in the central airways of smokers and interleukin-4 and -13 could contribute to mucus hypersecretion in chronic bronchitis.